292 SPECIFIC MICRO-ORGANISMS 



to find. The poison produced by the organisms is probably ab- 

 sorbed by the nerve endings^ and transmitted to the central nerv- 

 ous system through the axis cylinders or in the perineural lymph 

 spaces of the motor neurones rather than througlj the blood 

 stream. The symptoms arise after the poison reaches the central 

 nervous system in sufficient concentration to stimulate the nerve 

 cells. In guinea-pigs and mice the spasm always begins near the 

 point of inoculation, but in man and the large 'mammals it often 

 begins in the muscles of the jaw and neck regardless of the location 

 of the wound. Wassermann and Takaki have shown that o.i 



Pig. 116. — Tetanus bacilli showing terminal spores. {After Kolle and Wassermann.) 



gram of brain substance suspended in salt solution is able to neu- 

 tralize 10 fatal doses of tetanus toxin, forming a loose combina- 

 tion from which the toxin may be set free by drying. Most 

 mammals are very susceptible, although cats and dogs are only 

 slightly so. Birds are relatively resistant and some reptiles are 

 wholly refractory to the tetanus toxin. 



Von Behring and Kitasato in 1890 produced immunity in 

 rabbits, and later in horses, by injecting into them toxin to which 

 iodine trichloride had been added, and subsequently unaltered 

 toxin. The immunized animal was able to survive an injection 



1 Von Lingelsheim, Kolle and Wassermann, Handbuch, 191 2, Bd. IV, S. 766. 



